sys/cddl/contrib/opensolaris/uts/intel/dtrace/fasttrap_isa.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  *
  21  * Portions Copyright 2010 The FreeBSD Foundation
  22  *
  23  * $FreeBSD$
  24  */
  25
  26 /*
  27  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  28  * Use is subject to license terms.
  29  */
  30
  31 #ifdef illumos
  32 #pragma ident   "%Z%%M% %I%     %E% SMI"
  33 #endif
  34
  35 #include <sys/fasttrap_isa.h>
  36 #include <sys/fasttrap_impl.h>
  37 #include <sys/dtrace.h>
  38 #include <sys/dtrace_impl.h>
  39 #include <sys/cmn_err.h>
  40 #ifdef illumos
  41 #include <sys/regset.h>
  42 #include <sys/privregs.h>
  43 #include <sys/segments.h>
  44 #include <sys/x86_archext.h>
  45 #else
  46 #include <sys/types.h>
  47 #include <sys/dtrace_bsd.h>
  48 #include <sys/proc.h>
  49 #include <sys/rmlock.h>
  50 #include <cddl/dev/dtrace/dtrace_cddl.h>
  51 #include <cddl/dev/dtrace/x86/regset.h>
  52 #include <machine/segments.h>
  53 #include <machine/reg.h>
  54 #include <machine/pcb.h>
  55 #endif
  56 #include <sys/sysmacros.h>
  57 #ifdef illumos
  58 #include <sys/trap.h>
  59 #include <sys/archsystm.h>
  60 #else
  61 #include <sys/ptrace.h>
  62 #endif /* illumos */
  63
  64 #ifdef __i386__
  65 #define r_rax   r_eax
  66 #define r_rbx   r_ebx
  67 #define r_rip   r_eip
  68 #define r_rflags r_eflags
  69 #define r_rsp   r_esp
  70 #define r_rbp   r_ebp
  71 #endif
  72
  73 /*
  74  * Lossless User-Land Tracing on x86
  75  * ---------------------------------
  76  *
  77  * The execution of most instructions is not dependent on the address; for
  78  * these instructions it is sufficient to copy them into the user process's
  79  * address space and execute them. To effectively single-step an instruction
  80  * in user-land, we copy out the following sequence of instructions to scratch
  81  * space in the user thread's ulwp_t structure.
  82  *
  83  * We then set the program counter (%eip or %rip) to point to this scratch
  84  * space. Once execution resumes, the original instruction is executed and
  85  * then control flow is redirected to what was originally the subsequent
  86  * instruction. If the kernel attemps to deliver a signal while single-
  87  * stepping, the signal is deferred and the program counter is moved into the
  88  * second sequence of instructions. The second sequence ends in a trap into
  89  * the kernel where the deferred signal is then properly handled and delivered.
  90  *
  91  * For instructions whose execute is position dependent, we perform simple
  92  * emulation. These instructions are limited to control transfer
  93  * instructions in 32-bit mode, but in 64-bit mode there's the added wrinkle
  94  * of %rip-relative addressing that means that almost any instruction can be
  95  * position dependent. For all the details on how we emulate generic
  96  * instructions included %rip-relative instructions, see the code in
  97  * fasttrap_pid_probe() below where we handle instructions of type
  98  * FASTTRAP_T_COMMON (under the header: Generic Instruction Tracing).
  99  */
 100
 101 #define FASTTRAP_MODRM_MOD(modrm)       (((modrm) >> 6) & 0x3)
 102 #define FASTTRAP_MODRM_REG(modrm)       (((modrm) >> 3) & 0x7)
 103 #define FASTTRAP_MODRM_RM(modrm)        ((modrm) & 0x7)
 104 #define FASTTRAP_MODRM(mod, reg, rm)    (((mod) << 6) | ((reg) << 3) | (rm))
 105
 106 #define FASTTRAP_SIB_SCALE(sib)         (((sib) >> 6) & 0x3)
 107 #define FASTTRAP_SIB_INDEX(sib)         (((sib) >> 3) & 0x7)
 108 #define FASTTRAP_SIB_BASE(sib)          ((sib) & 0x7)
 109
 110 #define FASTTRAP_REX_W(rex)             (((rex) >> 3) & 1)
 111 #define FASTTRAP_REX_R(rex)             (((rex) >> 2) & 1)
 112 #define FASTTRAP_REX_X(rex)             (((rex) >> 1) & 1)
 113 #define FASTTRAP_REX_B(rex)             ((rex) & 1)
 114 #define FASTTRAP_REX(w, r, x, b)        \
 115         (0x40 | ((w) << 3) | ((r) << 2) | ((x) << 1) | (b))
 116
 117 /*
 118  * Single-byte op-codes.
 119  */
 120 #define FASTTRAP_PUSHL_EBP      0x55
 121
 122 #define FASTTRAP_JO             0x70
 123 #define FASTTRAP_JNO            0x71
 124 #define FASTTRAP_JB             0x72
 125 #define FASTTRAP_JAE            0x73
 126 #define FASTTRAP_JE             0x74
 127 #define FASTTRAP_JNE            0x75
 128 #define FASTTRAP_JBE            0x76
 129 #define FASTTRAP_JA             0x77
 130 #define FASTTRAP_JS             0x78
 131 #define FASTTRAP_JNS            0x79
 132 #define FASTTRAP_JP             0x7a
 133 #define FASTTRAP_JNP            0x7b
 134 #define FASTTRAP_JL             0x7c
 135 #define FASTTRAP_JGE            0x7d
 136 #define FASTTRAP_JLE            0x7e
 137 #define FASTTRAP_JG             0x7f
 138
 139 #define FASTTRAP_NOP            0x90
 140
 141 #define FASTTRAP_MOV_EAX        0xb8
 142 #define FASTTRAP_MOV_ECX        0xb9
 143
 144 #define FASTTRAP_RET16          0xc2
 145 #define FASTTRAP_RET            0xc3
 146
 147 #define FASTTRAP_LOOPNZ         0xe0
 148 #define FASTTRAP_LOOPZ          0xe1
 149 #define FASTTRAP_LOOP           0xe2
 150 #define FASTTRAP_JCXZ           0xe3
 151
 152 #define FASTTRAP_CALL           0xe8
 153 #define FASTTRAP_JMP32          0xe9
 154 #define FASTTRAP_JMP8           0xeb
 155
 156 #define FASTTRAP_INT3           0xcc
 157 #define FASTTRAP_INT            0xcd
 158
 159 #define FASTTRAP_2_BYTE_OP      0x0f
 160 #define FASTTRAP_GROUP5_OP      0xff
 161
 162 /*
 163  * Two-byte op-codes (second byte only).
 164  */
 165 #define FASTTRAP_0F_JO          0x80
 166 #define FASTTRAP_0F_JNO         0x81
 167 #define FASTTRAP_0F_JB          0x82
 168 #define FASTTRAP_0F_JAE         0x83
 169 #define FASTTRAP_0F_JE          0x84
 170 #define FASTTRAP_0F_JNE         0x85
 171 #define FASTTRAP_0F_JBE         0x86
 172 #define FASTTRAP_0F_JA          0x87
 173 #define FASTTRAP_0F_JS          0x88
 174 #define FASTTRAP_0F_JNS         0x89
 175 #define FASTTRAP_0F_JP          0x8a
 176 #define FASTTRAP_0F_JNP         0x8b
 177 #define FASTTRAP_0F_JL          0x8c
 178 #define FASTTRAP_0F_JGE         0x8d
 179 #define FASTTRAP_0F_JLE         0x8e
 180 #define FASTTRAP_0F_JG          0x8f
 181
 182 #define FASTTRAP_EFLAGS_OF      0x800
 183 #define FASTTRAP_EFLAGS_DF      0x400
 184 #define FASTTRAP_EFLAGS_SF      0x080
 185 #define FASTTRAP_EFLAGS_ZF      0x040
 186 #define FASTTRAP_EFLAGS_AF      0x010
 187 #define FASTTRAP_EFLAGS_PF      0x004
 188 #define FASTTRAP_EFLAGS_CF      0x001
 189
 190 /*
 191  * Instruction prefixes.
 192  */
 193 #define FASTTRAP_PREFIX_OPERAND 0x66
 194 #define FASTTRAP_PREFIX_ADDRESS 0x67
 195 #define FASTTRAP_PREFIX_CS      0x2E
 196 #define FASTTRAP_PREFIX_DS      0x3E
 197 #define FASTTRAP_PREFIX_ES      0x26
 198 #define FASTTRAP_PREFIX_FS      0x64
 199 #define FASTTRAP_PREFIX_GS      0x65
 200 #define FASTTRAP_PREFIX_SS      0x36
 201 #define FASTTRAP_PREFIX_LOCK    0xF0
 202 #define FASTTRAP_PREFIX_REP     0xF3
 203 #define FASTTRAP_PREFIX_REPNE   0xF2
 204
 205 #define FASTTRAP_NOREG  0xff
 206
 207 /*
 208  * Map between instruction register encodings and the kernel constants which
 209  * correspond to indicies into struct regs.
 210  */
 211 #ifdef __amd64
 212 static const uint8_t regmap[16] = {
 213         REG_RAX, REG_RCX, REG_RDX, REG_RBX, REG_RSP, REG_RBP, REG_RSI, REG_RDI,
 214         REG_R8, REG_R9, REG_R10, REG_R11, REG_R12, REG_R13, REG_R14, REG_R15,
 215 };
 216 #else
 217 static const uint8_t regmap[8] = {
 218         EAX, ECX, EDX, EBX, UESP, EBP, ESI, EDI
 219 };
 220 #endif
 221
 222 static ulong_t fasttrap_getreg(struct reg *, uint_t);
 223
 224 static uint64_t
 225 fasttrap_anarg(struct reg *rp, int function_entry, int argno)
 226 {
 227         uint64_t value = 0;
 228         int shift = function_entry ? 1 : 0;
 229
 230 #ifdef __amd64
 231         if (curproc->p_model == DATAMODEL_LP64) {
 232                 uintptr_t *stack;
 233
 234                 /*
 235                  * In 64-bit mode, the first six arguments are stored in
 236                  * registers.
 237                  */
 238                 if (argno < 6)
 239                         switch (argno) {
 240                         case 0:
 241                                 return (rp->r_rdi);
 242                         case 1:
 243                                 return (rp->r_rsi);
 244                         case 2:
 245                                 return (rp->r_rdx);
 246                         case 3:
 247                                 return (rp->r_rcx);
 248                         case 4:
 249                                 return (rp->r_r8);
 250                         case 5:
 251                                 return (rp->r_r9);
 252                         }
 253
 254                 stack = (uintptr_t *)rp->r_rsp;
 255                 DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
 256                 value = dtrace_fulword(&stack[argno - 6 + shift]);
 257                 DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT | CPU_DTRACE_BADADDR);
 258         } else {
 259 #endif
 260                 uint32_t *stack = (uint32_t *)rp->r_rsp;
 261                 DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
 262                 value = dtrace_fuword32(&stack[argno + shift]);
 263                 DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT | CPU_DTRACE_BADADDR);
 264 #ifdef __amd64
 265         }
 266 #endif
 267
 268         return (value);
 269 }
 270
 271 /*ARGSUSED*/
 272 int
 273 fasttrap_tracepoint_init(proc_t *p, fasttrap_tracepoint_t *tp, uintptr_t pc,
 274     fasttrap_probe_type_t type)
 275 {
 276         uint8_t instr[FASTTRAP_MAX_INSTR_SIZE + 10];
 277         size_t len = FASTTRAP_MAX_INSTR_SIZE;
 278         size_t first = MIN(len, PAGESIZE - (pc & PAGEOFFSET));
 279         uint_t start = 0;
 280         int rmindex, size;
 281         uint8_t seg, rex = 0;
 282
 283         /*
 284          * Read the instruction at the given address out of the process's
 285          * address space. We don't have to worry about a debugger
 286          * changing this instruction before we overwrite it with our trap
 287          * instruction since P_PR_LOCK is set. Since instructions can span
 288          * pages, we potentially read the instruction in two parts. If the
 289          * second part fails, we just zero out that part of the instruction.
 290          */
 291         if (uread(p, &instr[0], first, pc) != 0)
 292                 return (-1);
 293         if (len > first &&
 294             uread(p, &instr[first], len - first, pc + first) != 0) {
 295                 bzero(&instr[first], len - first);
 296                 len = first;
 297         }
 298
 299         /*
 300          * If the disassembly fails, then we have a malformed instruction.
 301          */
 302         if ((size = dtrace_instr_size_isa(instr, p->p_model, &rmindex)) <= 0)
 303                 return (-1);
 304
 305         /*
 306          * Make sure the disassembler isn't completely broken.
 307          */
 308         ASSERT(-1 <= rmindex && rmindex < size);
 309
 310         /*
 311          * If the computed size is greater than the number of bytes read,
 312          * then it was a malformed instruction possibly because it fell on a
 313          * page boundary and the subsequent page was missing or because of
 314          * some malicious user.
 315          */
 316         if (size > len)
 317                 return (-1);
 318
 319         tp->ftt_size = (uint8_t)size;
 320         tp->ftt_segment = FASTTRAP_SEG_NONE;
 321
 322         /*
 323          * Find the start of the instruction's opcode by processing any
 324          * legacy prefixes.
 325          */
 326         for (;;) {
 327                 seg = 0;
 328                 switch (instr[start]) {
 329                 case FASTTRAP_PREFIX_SS:
 330                         seg++;
 331                         /*FALLTHRU*/
 332                 case FASTTRAP_PREFIX_GS:
 333                         seg++;
 334                         /*FALLTHRU*/
 335                 case FASTTRAP_PREFIX_FS:
 336                         seg++;
 337                         /*FALLTHRU*/
 338                 case FASTTRAP_PREFIX_ES:
 339                         seg++;
 340                         /*FALLTHRU*/
 341                 case FASTTRAP_PREFIX_DS:
 342                         seg++;
 343                         /*FALLTHRU*/
 344                 case FASTTRAP_PREFIX_CS:
 345                         seg++;
 346                         /*FALLTHRU*/
 347                 case FASTTRAP_PREFIX_OPERAND:
 348                 case FASTTRAP_PREFIX_ADDRESS:
 349                 case FASTTRAP_PREFIX_LOCK:
 350                 case FASTTRAP_PREFIX_REP:
 351                 case FASTTRAP_PREFIX_REPNE:
 352                         if (seg != 0) {
 353                                 /*
 354                                  * It's illegal for an instruction to specify
 355                                  * two segment prefixes -- give up on this
 356                                  * illegal instruction.
 357                                  */
 358                                 if (tp->ftt_segment != FASTTRAP_SEG_NONE)
 359                                         return (-1);
 360
 361                                 tp->ftt_segment = seg;
 362                         }
 363                         start++;
 364                         continue;
 365                 }
 366                 break;
 367         }
 368
 369 #ifdef __amd64
 370         /*
 371          * Identify the REX prefix on 64-bit processes.
 372          */
 373         if (p->p_model == DATAMODEL_LP64 && (instr[start] & 0xf0) == 0x40)
 374                 rex = instr[start++];
 375 #endif
 376
 377         /*
 378          * Now that we're pretty sure that the instruction is okay, copy the
 379          * valid part to the tracepoint.
 380          */
 381         bcopy(instr, tp->ftt_instr, FASTTRAP_MAX_INSTR_SIZE);
 382
 383         tp->ftt_type = FASTTRAP_T_COMMON;
 384         if (instr[start] == FASTTRAP_2_BYTE_OP) {
 385                 switch (instr[start + 1]) {
 386                 case FASTTRAP_0F_JO:
 387                 case FASTTRAP_0F_JNO:
 388                 case FASTTRAP_0F_JB:
 389                 case FASTTRAP_0F_JAE:
 390                 case FASTTRAP_0F_JE:
 391                 case FASTTRAP_0F_JNE:
 392                 case FASTTRAP_0F_JBE:
 393                 case FASTTRAP_0F_JA:
 394                 case FASTTRAP_0F_JS:
 395                 case FASTTRAP_0F_JNS:
 396                 case FASTTRAP_0F_JP:
 397                 case FASTTRAP_0F_JNP:
 398                 case FASTTRAP_0F_JL:
 399                 case FASTTRAP_0F_JGE:
 400                 case FASTTRAP_0F_JLE:
 401                 case FASTTRAP_0F_JG:
 402                         tp->ftt_type = FASTTRAP_T_JCC;
 403                         tp->ftt_code = (instr[start + 1] & 0x0f) | FASTTRAP_JO;
 404                         tp->ftt_dest = pc + tp->ftt_size +
 405                             /* LINTED - alignment */
 406                             *(int32_t *)&instr[start + 2];
 407                         break;
 408                 }
 409         } else if (instr[start] == FASTTRAP_GROUP5_OP) {
 410                 uint_t mod = FASTTRAP_MODRM_MOD(instr[start + 1]);
 411                 uint_t reg = FASTTRAP_MODRM_REG(instr[start + 1]);
 412                 uint_t rm = FASTTRAP_MODRM_RM(instr[start + 1]);
 413
 414                 if (reg == 2 || reg == 4) {
 415                         uint_t i, sz;
 416
 417                         if (reg == 2)
 418                                 tp->ftt_type = FASTTRAP_T_CALL;
 419                         else
 420                                 tp->ftt_type = FASTTRAP_T_JMP;
 421
 422                         if (mod == 3)
 423                                 tp->ftt_code = 2;
 424                         else
 425                                 tp->ftt_code = 1;
 426
 427                         ASSERT(p->p_model == DATAMODEL_LP64 || rex == 0);
 428
 429                         /*
 430                          * See AMD x86-64 Architecture Programmer's Manual
 431                          * Volume 3, Section 1.2.7, Table 1-12, and
 432                          * Appendix A.3.1, Table A-15.
 433                          */
 434                         if (mod != 3 && rm == 4) {
 435                                 uint8_t sib = instr[start + 2];
 436                                 uint_t index = FASTTRAP_SIB_INDEX(sib);
 437                                 uint_t base = FASTTRAP_SIB_BASE(sib);
 438
 439                                 tp->ftt_scale = FASTTRAP_SIB_SCALE(sib);
 440
 441                                 tp->ftt_index = (index == 4) ?
 442                                     FASTTRAP_NOREG :
 443                                     regmap[index | (FASTTRAP_REX_X(rex) << 3)];
 444                                 tp->ftt_base = (mod == 0 && base == 5) ?
 445                                     FASTTRAP_NOREG :
 446                                     regmap[base | (FASTTRAP_REX_B(rex) << 3)];
 447
 448                                 i = 3;
 449                                 sz = mod == 1 ? 1 : 4;
 450                         } else {
 451                                 /*
 452                                  * In 64-bit mode, mod == 0 and r/m == 5
 453                                  * denotes %rip-relative addressing; in 32-bit
 454                                  * mode, the base register isn't used. In both
 455                                  * modes, there is a 32-bit operand.
 456                                  */
 457                                 if (mod == 0 && rm == 5) {
 458 #ifdef __amd64
 459                                         if (p->p_model == DATAMODEL_LP64)
 460                                                 tp->ftt_base = REG_RIP;
 461                                         else
 462 #endif
 463                                                 tp->ftt_base = FASTTRAP_NOREG;
 464                                         sz = 4;
 465                                 } else  {
 466                                         uint8_t base = rm |
 467                                             (FASTTRAP_REX_B(rex) << 3);
 468
 469                                         tp->ftt_base = regmap[base];
 470                                         sz = mod == 1 ? 1 : mod == 2 ? 4 : 0;
 471                                 }
 472                                 tp->ftt_index = FASTTRAP_NOREG;
 473                                 i = 2;
 474                         }
 475
 476                         if (sz == 1) {
 477                                 tp->ftt_dest = *(int8_t *)&instr[start + i];
 478                         } else if (sz == 4) {
 479                                 /* LINTED - alignment */
 480                                 tp->ftt_dest = *(int32_t *)&instr[start + i];
 481                         } else {
 482                                 tp->ftt_dest = 0;
 483                         }
 484                 }
 485         } else {
 486                 switch (instr[start]) {
 487                 case FASTTRAP_RET:
 488                         tp->ftt_type = FASTTRAP_T_RET;
 489                         break;
 490
 491                 case FASTTRAP_RET16:
 492                         tp->ftt_type = FASTTRAP_T_RET16;
 493                         /* LINTED - alignment */
 494                         tp->ftt_dest = *(uint16_t *)&instr[start + 1];
 495                         break;
 496
 497                 case FASTTRAP_JO:
 498                 case FASTTRAP_JNO:
 499                 case FASTTRAP_JB:
 500                 case FASTTRAP_JAE:
 501                 case FASTTRAP_JE:
 502                 case FASTTRAP_JNE:
 503                 case FASTTRAP_JBE:
 504                 case FASTTRAP_JA:
 505                 case FASTTRAP_JS:
 506                 case FASTTRAP_JNS:
 507                 case FASTTRAP_JP:
 508                 case FASTTRAP_JNP:
 509                 case FASTTRAP_JL:
 510                 case FASTTRAP_JGE:
 511                 case FASTTRAP_JLE:
 512                 case FASTTRAP_JG:
 513                         tp->ftt_type = FASTTRAP_T_JCC;
 514                         tp->ftt_code = instr[start];
 515                         tp->ftt_dest = pc + tp->ftt_size +
 516                             (int8_t)instr[start + 1];
 517                         break;
 518
 519                 case FASTTRAP_LOOPNZ:
 520                 case FASTTRAP_LOOPZ:
 521                 case FASTTRAP_LOOP:
 522                         tp->ftt_type = FASTTRAP_T_LOOP;
 523                         tp->ftt_code = instr[start];
 524                         tp->ftt_dest = pc + tp->ftt_size +
 525                             (int8_t)instr[start + 1];
 526                         break;
 527
 528                 case FASTTRAP_JCXZ:
 529                         tp->ftt_type = FASTTRAP_T_JCXZ;
 530                         tp->ftt_dest = pc + tp->ftt_size +
 531                             (int8_t)instr[start + 1];
 532                         break;
 533
 534                 case FASTTRAP_CALL:
 535                         tp->ftt_type = FASTTRAP_T_CALL;
 536                         tp->ftt_dest = pc + tp->ftt_size +
 537                             /* LINTED - alignment */
 538                             *(int32_t *)&instr[start + 1];
 539                         tp->ftt_code = 0;
 540                         break;
 541
 542                 case FASTTRAP_JMP32:
 543                         tp->ftt_type = FASTTRAP_T_JMP;
 544                         tp->ftt_dest = pc + tp->ftt_size +
 545                             /* LINTED - alignment */
 546                             *(int32_t *)&instr[start + 1];
 547                         break;
 548                 case FASTTRAP_JMP8:
 549                         tp->ftt_type = FASTTRAP_T_JMP;
 550                         tp->ftt_dest = pc + tp->ftt_size +
 551                             (int8_t)instr[start + 1];
 552                         break;
 553
 554                 case FASTTRAP_PUSHL_EBP:
 555                         if (start == 0)
 556                                 tp->ftt_type = FASTTRAP_T_PUSHL_EBP;
 557                         break;
 558
 559                 case FASTTRAP_NOP:
 560 #ifdef __amd64
 561                         ASSERT(p->p_model == DATAMODEL_LP64 || rex == 0);
 562
 563                         /*
 564                          * On amd64 we have to be careful not to confuse a nop
 565                          * (actually xchgl %eax, %eax) with an instruction using
 566                          * the same opcode, but that does something different
 567                          * (e.g. xchgl %r8d, %eax or xcghq %r8, %rax).
 568                          */
 569                         if (FASTTRAP_REX_B(rex) == 0)
 570 #endif
 571                                 tp->ftt_type = FASTTRAP_T_NOP;
 572                         break;
 573
 574                 case FASTTRAP_INT3:
 575                         /*
 576                          * The pid provider shares the int3 trap with debugger
 577                          * breakpoints so we can't instrument them.
 578                          */
 579                         ASSERT(instr[start] == FASTTRAP_INSTR);
 580                         return (-1);
 581
 582                 case FASTTRAP_INT:
 583                         /*
 584                          * Interrupts seem like they could be traced with
 585                          * no negative implications, but it's possible that
 586                          * a thread could be redirected by the trap handling
 587                          * code which would eventually return to the
 588                          * instruction after the interrupt. If the interrupt
 589                          * were in our scratch space, the subsequent
 590                          * instruction might be overwritten before we return.
 591                          * Accordingly we refuse to instrument any interrupt.
 592                          */
 593                         return (-1);
 594                 }
 595         }
 596
 597 #ifdef __amd64
 598         if (p->p_model == DATAMODEL_LP64 && tp->ftt_type == FASTTRAP_T_COMMON) {
 599                 /*
 600                  * If the process is 64-bit and the instruction type is still
 601                  * FASTTRAP_T_COMMON -- meaning we're going to copy it out an
 602                  * execute it -- we need to watch for %rip-relative
 603                  * addressing mode. See the portion of fasttrap_pid_probe()
 604                  * below where we handle tracepoints with type
 605                  * FASTTRAP_T_COMMON for how we emulate instructions that
 606                  * employ %rip-relative addressing.
 607                  */
 608                 if (rmindex != -1) {
 609                         uint_t mod = FASTTRAP_MODRM_MOD(instr[rmindex]);
 610                         uint_t reg = FASTTRAP_MODRM_REG(instr[rmindex]);
 611                         uint_t rm = FASTTRAP_MODRM_RM(instr[rmindex]);
 612
 613                         ASSERT(rmindex > start);
 614
 615                         if (mod == 0 && rm == 5) {
 616                                 /*
 617                                  * We need to be sure to avoid other
 618                                  * registers used by this instruction. While
 619                                  * the reg field may determine the op code
 620                                  * rather than denoting a register, assuming
 621                                  * that it denotes a register is always safe.
 622                                  * We leave the REX field intact and use
 623                                  * whatever value's there for simplicity.
 624                                  */
 625                                 if (reg != 0) {
 626                                         tp->ftt_ripmode = FASTTRAP_RIP_1 |
 627                                             (FASTTRAP_RIP_X *
 628                                             FASTTRAP_REX_B(rex));
 629                                         rm = 0;
 630                                 } else {
 631                                         tp->ftt_ripmode = FASTTRAP_RIP_2 |
 632                                             (FASTTRAP_RIP_X *
 633                                             FASTTRAP_REX_B(rex));
 634                                         rm = 1;
 635                                 }
 636
 637                                 tp->ftt_modrm = tp->ftt_instr[rmindex];
 638                                 tp->ftt_instr[rmindex] =
 639                                     FASTTRAP_MODRM(2, reg, rm);
 640                         }
 641                 }
 642         }
 643 #endif
 644
 645         return (0);
 646 }
 647
 648 int
 649 fasttrap_tracepoint_install(proc_t *p, fasttrap_tracepoint_t *tp)
 650 {
 651         fasttrap_instr_t instr = FASTTRAP_INSTR;
 652
 653         if (uwrite(p, &instr, 1, tp->ftt_pc) != 0)
 654                 return (-1);
 655
 656         return (0);
 657 }
 658
 659 int
 660 fasttrap_tracepoint_remove(proc_t *p, fasttrap_tracepoint_t *tp)
 661 {
 662         uint8_t instr;
 663
 664         /*
 665          * Distinguish between read or write failures and a changed
 666          * instruction.
 667          */
 668         if (uread(p, &instr, 1, tp->ftt_pc) != 0)
 669                 return (0);
 670         if (instr != FASTTRAP_INSTR)
 671                 return (0);
 672         if (uwrite(p, &tp->ftt_instr[0], 1, tp->ftt_pc) != 0)
 673                 return (-1);
 674
 675         return (0);
 676 }
 677
 678 #ifdef __amd64
 679 static uintptr_t
 680 fasttrap_fulword_noerr(const void *uaddr)
 681 {
 682         uintptr_t ret;
 683
 684         if ((ret = fasttrap_fulword(uaddr)) != -1)
 685                 return (ret);
 686
 687         return (0);
 688 }
 689 #endif
 690
 691 static uint32_t
 692 fasttrap_fuword32_noerr(const void *uaddr)
 693 {
 694         uint32_t ret;
 695
 696         if ((ret = fasttrap_fuword32(uaddr)) != -1)
 697                 return (ret);
 698
 699         return (0);
 700 }
 701
 702 static void
 703 fasttrap_return_common(struct reg *rp, uintptr_t pc, pid_t pid,
 704     uintptr_t new_pc)
 705 {
 706         fasttrap_tracepoint_t *tp;
 707         fasttrap_bucket_t *bucket;
 708         fasttrap_id_t *id;
 709 #ifdef illumos
 710         kmutex_t *pid_mtx;
 711
 712         pid_mtx = &cpu_core[CPU->cpu_id].cpuc_pid_lock;
 713         mutex_enter(pid_mtx);
 714 #else
 715         struct rm_priotracker tracker;
 716
 717         rm_rlock(&fasttrap_tp_lock, &tracker);
 718 #endif
 719         bucket = &fasttrap_tpoints.fth_table[FASTTRAP_TPOINTS_INDEX(pid, pc)];
 720
 721         for (tp = bucket->ftb_data; tp != NULL; tp = tp->ftt_next) {
 722                 if (pid == tp->ftt_pid && pc == tp->ftt_pc &&
 723                     tp->ftt_proc->ftpc_acount != 0)
 724                         break;
 725         }
 726
 727         /*
 728          * Don't sweat it if we can't find the tracepoint again; unlike
 729          * when we're in fasttrap_pid_probe(), finding the tracepoint here
 730          * is not essential to the correct execution of the process.
 731          */
 732         if (tp == NULL) {
 733 #ifdef illumos
 734                 mutex_exit(pid_mtx);
 735 #else
 736                 rm_runlock(&fasttrap_tp_lock, &tracker);
 737 #endif
 738                 return;
 739         }
 740
 741         for (id = tp->ftt_retids; id != NULL; id = id->fti_next) {
 742                 /*
 743                  * If there's a branch that could act as a return site, we
 744                  * need to trace it, and check here if the program counter is
 745                  * external to the function.
 746                  */
 747                 if (tp->ftt_type != FASTTRAP_T_RET &&
 748                     tp->ftt_type != FASTTRAP_T_RET16 &&
 749                     new_pc - id->fti_probe->ftp_faddr <
 750                     id->fti_probe->ftp_fsize)
 751                         continue;
 752
 753                 dtrace_probe(id->fti_probe->ftp_id,
 754                     pc - id->fti_probe->ftp_faddr,
 755                     rp->r_rax, rp->r_rbx, 0, 0);
 756         }
 757
 758 #ifdef illumos
 759         mutex_exit(pid_mtx);
 760 #else
 761         rm_runlock(&fasttrap_tp_lock, &tracker);
 762 #endif
 763 }
 764
 765 static void
 766 fasttrap_sigsegv(proc_t *p, kthread_t *t, uintptr_t addr)
 767 {
 768 #ifdef illumos
 769         sigqueue_t *sqp = kmem_zalloc(sizeof (sigqueue_t), KM_SLEEP);
 770
 771         sqp->sq_info.si_signo = SIGSEGV;
 772         sqp->sq_info.si_code = SEGV_MAPERR;
 773         sqp->sq_info.si_addr = (caddr_t)addr;
 774
 775         mutex_enter(&p->p_lock);
 776         sigaddqa(p, t, sqp);
 777         mutex_exit(&p->p_lock);
 778
 779         if (t != NULL)
 780                 aston(t);
 781 #else
 782         ksiginfo_t *ksi = kmem_zalloc(sizeof (ksiginfo_t), KM_SLEEP);
 783
 784         ksiginfo_init(ksi);
 785         ksi->ksi_signo = SIGSEGV;
 786         ksi->ksi_code = SEGV_MAPERR;
 787         ksi->ksi_addr = (caddr_t)addr;
 788         (void) tdksignal(t, SIGSEGV, ksi);
 789 #endif
 790 }
 791
 792 #ifdef __amd64
 793 static void
 794 fasttrap_usdt_args64(fasttrap_probe_t *probe, struct reg *rp, int argc,
 795     uintptr_t *argv)
 796 {
 797         int i, x, cap = MIN(argc, probe->ftp_nargs);
 798         uintptr_t *stack = (uintptr_t *)rp->r_rsp;
 799
 800         for (i = 0; i < cap; i++) {
 801                 x = probe->ftp_argmap[i];
 802
 803                 if (x < 6)
 804                         argv[i] = (&rp->r_rdi)[x];
 805                 else
 806                         argv[i] = fasttrap_fulword_noerr(&stack[x]);
 807         }
 808
 809         for (; i < argc; i++) {
 810                 argv[i] = 0;
 811         }
 812 }
 813 #endif
 814
 815 static void
 816 fasttrap_usdt_args32(fasttrap_probe_t *probe, struct reg *rp, int argc,
 817     uint32_t *argv)
 818 {
 819         int i, x, cap = MIN(argc, probe->ftp_nargs);
 820         uint32_t *stack = (uint32_t *)rp->r_rsp;
 821
 822         for (i = 0; i < cap; i++) {
 823                 x = probe->ftp_argmap[i];
 824
 825                 argv[i] = fasttrap_fuword32_noerr(&stack[x]);
 826         }
 827
 828         for (; i < argc; i++) {
 829                 argv[i] = 0;
 830         }
 831 }
 832
 833 static int
 834 fasttrap_do_seg(fasttrap_tracepoint_t *tp, struct reg *rp, uintptr_t *addr)
 835 {
 836         proc_t *p = curproc;
 837 #ifdef __i386__
 838         struct segment_descriptor *desc;
 839 #else
 840         struct user_segment_descriptor *desc;
 841 #endif
 842         uint16_t sel = 0, ndx, type;
 843         uintptr_t limit;
 844
 845         switch (tp->ftt_segment) {
 846         case FASTTRAP_SEG_CS:
 847                 sel = rp->r_cs;
 848                 break;
 849         case FASTTRAP_SEG_DS:
 850                 sel = rp->r_ds;
 851                 break;
 852         case FASTTRAP_SEG_ES:
 853                 sel = rp->r_es;
 854                 break;
 855         case FASTTRAP_SEG_FS:
 856                 sel = rp->r_fs;
 857                 break;
 858         case FASTTRAP_SEG_GS:
 859                 sel = rp->r_gs;
 860                 break;
 861         case FASTTRAP_SEG_SS:
 862                 sel = rp->r_ss;
 863                 break;
 864         }
 865
 866         /*
 867          * Make sure the given segment register specifies a user priority
 868          * selector rather than a kernel selector.
 869          */
 870         if (ISPL(sel) != SEL_UPL)
 871                 return (-1);
 872
 873         ndx = IDXSEL(sel);
 874
 875         /*
 876          * Check the bounds and grab the descriptor out of the specified
 877          * descriptor table.
 878          */
 879         if (ISLDT(sel)) {
 880 #ifdef __i386__
 881                 if (ndx > p->p_md.md_ldt->ldt_len)
 882                         return (-1);
 883
 884                 desc = (struct segment_descriptor *)
 885                     p->p_md.md_ldt[ndx].ldt_base;
 886 #else
 887                 if (ndx > max_ldt_segment)
 888                         return (-1);
 889
 890                 desc = (struct user_segment_descriptor *)
 891                     p->p_md.md_ldt[ndx].ldt_base;
 892 #endif
 893
 894         } else {
 895                 if (ndx >= NGDT)
 896                         return (-1);
 897
 898 #ifdef __i386__
 899                 desc = &gdt[ndx].sd;
 900 #else
 901                 desc = &gdt[ndx];
 902 #endif
 903         }
 904
 905         /*
 906          * The descriptor must have user privilege level and it must be
 907          * present in memory.
 908          */
 909         if (desc->sd_dpl != SEL_UPL || desc->sd_p != 1)
 910                 return (-1);
 911
 912         type = desc->sd_type;
 913
 914         /*
 915          * If the S bit in the type field is not set, this descriptor can
 916          * only be used in system context.
 917          */
 918         if ((type & 0x10) != 0x10)
 919                 return (-1);
 920
 921         limit = USD_GETLIMIT(desc) * (desc->sd_gran ? PAGESIZE : 1);
 922
 923         if (tp->ftt_segment == FASTTRAP_SEG_CS) {
 924                 /*
 925                  * The code/data bit and readable bit must both be set.
 926                  */
 927                 if ((type & 0xa) != 0xa)
 928                         return (-1);
 929
 930                 if (*addr > limit)
 931                         return (-1);
 932         } else {
 933                 /*
 934                  * The code/data bit must be clear.
 935                  */
 936                 if ((type & 0x8) != 0)
 937                         return (-1);
 938
 939                 /*
 940                  * If the expand-down bit is clear, we just check the limit as
 941                  * it would naturally be applied. Otherwise, we need to check
 942                  * that the address is the range [limit + 1 .. 0xffff] or
 943                  * [limit + 1 ... 0xffffffff] depending on if the default
 944                  * operand size bit is set.
 945                  */
 946                 if ((type & 0x4) == 0) {
 947                         if (*addr > limit)
 948                                 return (-1);
 949                 } else if (desc->sd_def32) {
 950                         if (*addr < limit + 1 || 0xffff < *addr)
 951                                 return (-1);
 952                 } else {
 953                         if (*addr < limit + 1 || 0xffffffff < *addr)
 954                                 return (-1);
 955                 }
 956         }
 957
 958         *addr += USD_GETBASE(desc);
 959
 960         return (0);
 961 }
 962
 963 int
 964 fasttrap_pid_probe(struct reg *rp)
 965 {
 966         proc_t *p = curproc;
 967 #ifndef illumos
 968         struct rm_priotracker tracker;
 969         proc_t *pp;
 970 #endif
 971         uintptr_t pc = rp->r_rip - 1;
 972         uintptr_t new_pc = 0;
 973         fasttrap_bucket_t *bucket;
 974 #ifdef illumos
 975         kmutex_t *pid_mtx;
 976 #endif
 977         fasttrap_tracepoint_t *tp, tp_local;
 978         pid_t pid;
 979         dtrace_icookie_t cookie;
 980         uint_t is_enabled = 0;
 981
 982         /*
 983          * It's possible that a user (in a veritable orgy of bad planning)
 984          * could redirect this thread's flow of control before it reached the
 985          * return probe fasttrap. In this case we need to kill the process
 986          * since it's in a unrecoverable state.
 987          */
 988         if (curthread->t_dtrace_step) {
 989                 ASSERT(curthread->t_dtrace_on);
 990                 fasttrap_sigtrap(p, curthread, pc);
 991                 return (0);
 992         }
 993
 994         /*
 995          * Clear all user tracing flags.
 996          */
 997         curthread->t_dtrace_ft = 0;
 998         curthread->t_dtrace_pc = 0;
 999         curthread->t_dtrace_npc = 0;
1000         curthread->t_dtrace_scrpc = 0;
1001         curthread->t_dtrace_astpc = 0;
1002 #ifdef __amd64
1003         curthread->t_dtrace_regv = 0;
1004 #endif
1005
1006         /*
1007          * Treat a child created by a call to vfork(2) as if it were its
1008          * parent. We know that there's only one thread of control in such a
1009          * process: this one.
1010          */
1011 #ifdef illumos
1012         while (p->p_flag & SVFORK) {
1013                 p = p->p_parent;
1014         }
1015
1016         pid = p->p_pid;
1017         pid_mtx = &cpu_core[CPU->cpu_id].cpuc_pid_lock;
1018         mutex_enter(pid_mtx);
1019 #else
1020         pp = p;
1021         sx_slock(&proctree_lock);
1022         while (pp->p_vmspace == pp->p_pptr->p_vmspace)
1023                 pp = pp->p_pptr;
1024         pid = pp->p_pid;
1025         sx_sunlock(&proctree_lock);
1026         pp = NULL;
1027
1028         rm_rlock(&fasttrap_tp_lock, &tracker);
1029 #endif
1030
1031         bucket = &fasttrap_tpoints.fth_table[FASTTRAP_TPOINTS_INDEX(pid, pc)];
1032
1033         /*
1034          * Lookup the tracepoint that the process just hit.
1035          */
1036         for (tp = bucket->ftb_data; tp != NULL; tp = tp->ftt_next) {
1037                 if (pid == tp->ftt_pid && pc == tp->ftt_pc &&
1038                     tp->ftt_proc->ftpc_acount != 0)
1039                         break;
1040         }
1041
1042         /*
1043          * If we couldn't find a matching tracepoint, either a tracepoint has
1044          * been inserted without using the pid<pid> ioctl interface (see
1045          * fasttrap_ioctl), or somehow we have mislaid this tracepoint.
1046          */
1047         if (tp == NULL) {
1048 #ifdef illumos
1049                 mutex_exit(pid_mtx);
1050 #else
1051                 rm_runlock(&fasttrap_tp_lock, &tracker);
1052 #endif
1053                 return (-1);
1054         }
1055
1056         /*
1057          * Set the program counter to the address of the traced instruction
1058          * so that it looks right in ustack() output.
1059          */
1060         rp->r_rip = pc;
1061
1062         if (tp->ftt_ids != NULL) {
1063                 fasttrap_id_t *id;
1064
1065 #ifdef __amd64
1066                 if (p->p_model == DATAMODEL_LP64) {
1067                         for (id = tp->ftt_ids; id != NULL; id = id->fti_next) {
1068                                 fasttrap_probe_t *probe = id->fti_probe;
1069
1070                                 if (id->fti_ptype == DTFTP_ENTRY) {
1071                                         /*
1072                                          * We note that this was an entry
1073                                          * probe to help ustack() find the
1074                                          * first caller.
1075                                          */
1076                                         cookie = dtrace_interrupt_disable();
1077                                         DTRACE_CPUFLAG_SET(CPU_DTRACE_ENTRY);
1078                                         dtrace_probe(probe->ftp_id, rp->r_rdi,
1079                                             rp->r_rsi, rp->r_rdx, rp->r_rcx,
1080                                             rp->r_r8);
1081                                         DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_ENTRY);
1082                                         dtrace_interrupt_enable(cookie);
1083                                 } else if (id->fti_ptype == DTFTP_IS_ENABLED) {
1084                                         /*
1085                                          * Note that in this case, we don't
1086                                          * call dtrace_probe() since it's only
1087                                          * an artificial probe meant to change
1088                                          * the flow of control so that it
1089                                          * encounters the true probe.
1090                                          */
1091                                         is_enabled = 1;
1092                                 } else if (probe->ftp_argmap == NULL) {
1093                                         dtrace_probe(probe->ftp_id, rp->r_rdi,
1094                                             rp->r_rsi, rp->r_rdx, rp->r_rcx,
1095                                             rp->r_r8);
1096                                 } else {
1097                                         uintptr_t t[5];
1098
1099                                         fasttrap_usdt_args64(probe, rp,
1100                                             sizeof (t) / sizeof (t[0]), t);
1101
1102                                         dtrace_probe(probe->ftp_id, t[0], t[1],
1103                                             t[2], t[3], t[4]);
1104                                 }
1105                         }
1106                 } else {
1107 #endif
1108                         uintptr_t s0, s1, s2, s3, s4, s5;
1109                         uint32_t *stack = (uint32_t *)rp->r_rsp;
1110
1111                         /*
1112                          * In 32-bit mode, all arguments are passed on the
1113                          * stack. If this is a function entry probe, we need
1114                          * to skip the first entry on the stack as it
1115                          * represents the return address rather than a
1116                          * parameter to the function.
1117                          */
1118                         s0 = fasttrap_fuword32_noerr(&stack[0]);
1119                         s1 = fasttrap_fuword32_noerr(&stack[1]);
1120                         s2 = fasttrap_fuword32_noerr(&stack[2]);
1121                         s3 = fasttrap_fuword32_noerr(&stack[3]);
1122                         s4 = fasttrap_fuword32_noerr(&stack[4]);
1123                         s5 = fasttrap_fuword32_noerr(&stack[5]);
1124
1125                         for (id = tp->ftt_ids; id != NULL; id = id->fti_next) {
1126                                 fasttrap_probe_t *probe = id->fti_probe;
1127
1128                                 if (id->fti_ptype == DTFTP_ENTRY) {
1129                                         /*
1130                                          * We note that this was an entry
1131                                          * probe to help ustack() find the
1132                                          * first caller.
1133                                          */
1134                                         cookie = dtrace_interrupt_disable();
1135                                         DTRACE_CPUFLAG_SET(CPU_DTRACE_ENTRY);
1136                                         dtrace_probe(probe->ftp_id, s1, s2,
1137                                             s3, s4, s5);
1138                                         DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_ENTRY);
1139                                         dtrace_interrupt_enable(cookie);
1140                                 } else if (id->fti_ptype == DTFTP_IS_ENABLED) {
1141                                         /*
1142                                          * Note that in this case, we don't
1143                                          * call dtrace_probe() since it's only
1144                                          * an artificial probe meant to change
1145                                          * the flow of control so that it
1146                                          * encounters the true probe.
1147                                          */
1148                                         is_enabled = 1;
1149                                 } else if (probe->ftp_argmap == NULL) {
1150                                         dtrace_probe(probe->ftp_id, s0, s1,
1151                                             s2, s3, s4);
1152                                 } else {
1153                                         uint32_t t[5];
1154
1155                                         fasttrap_usdt_args32(probe, rp,
1156                                             sizeof (t) / sizeof (t[0]), t);
1157
1158                                         dtrace_probe(probe->ftp_id, t[0], t[1],
1159                                             t[2], t[3], t[4]);
1160                                 }
1161                         }
1162 #ifdef __amd64
1163                 }
1164 #endif
1165         }
1166
1167         /*
1168          * We're about to do a bunch of work so we cache a local copy of
1169          * the tracepoint to emulate the instruction, and then find the
1170          * tracepoint again later if we need to light up any return probes.
1171          */
1172         tp_local = *tp;
1173 #ifdef illumos
1174         mutex_exit(pid_mtx);
1175 #else
1176         rm_runlock(&fasttrap_tp_lock, &tracker);
1177 #endif
1178         tp = &tp_local;
1179
1180         /*
1181          * Set the program counter to appear as though the traced instruction
1182          * had completely executed. This ensures that fasttrap_getreg() will
1183          * report the expected value for REG_RIP.
1184          */
1185         rp->r_rip = pc + tp->ftt_size;
1186
1187         /*
1188          * If there's an is-enabled probe connected to this tracepoint it
1189          * means that there was a 'xorl %eax, %eax' or 'xorq %rax, %rax'
1190          * instruction that was placed there by DTrace when the binary was
1191          * linked. As this probe is, in fact, enabled, we need to stuff 1
1192          * into %eax or %rax. Accordingly, we can bypass all the instruction
1193          * emulation logic since we know the inevitable result. It's possible
1194          * that a user could construct a scenario where the 'is-enabled'
1195          * probe was on some other instruction, but that would be a rather
1196          * exotic way to shoot oneself in the foot.
1197          */
1198         if (is_enabled) {
1199                 rp->r_rax = 1;
1200                 new_pc = rp->r_rip;
1201                 goto done;
1202         }
1203
1204         /*
1205          * We emulate certain types of instructions to ensure correctness
1206          * (in the case of position dependent instructions) or optimize
1207          * common cases. The rest we have the thread execute back in user-
1208          * land.
1209          */
1210         switch (tp->ftt_type) {
1211         case FASTTRAP_T_RET:
1212         case FASTTRAP_T_RET16:
1213         {
1214                 uintptr_t dst = 0;
1215                 uintptr_t addr = 0;
1216                 int ret = 0;
1217
1218                 /*
1219                  * We have to emulate _every_ facet of the behavior of a ret
1220                  * instruction including what happens if the load from %esp
1221                  * fails; in that case, we send a SIGSEGV.
1222                  */
1223 #ifdef __amd64
1224                 if (p->p_model == DATAMODEL_NATIVE) {
1225                         ret = dst = fasttrap_fulword((void *)rp->r_rsp);
1226                         addr = rp->r_rsp + sizeof (uintptr_t);
1227                 } else {
1228 #endif
1229                         uint32_t dst32;
1230                         ret = dst32 = fasttrap_fuword32((void *)rp->r_rsp);
1231                         dst = dst32;
1232                         addr = rp->r_rsp + sizeof (uint32_t);
1233 #ifdef __amd64
1234                 }
1235 #endif
1236
1237                 if (ret == -1) {
1238                         fasttrap_sigsegv(p, curthread, rp->r_rsp);
1239                         new_pc = pc;
1240                         break;
1241                 }
1242
1243                 if (tp->ftt_type == FASTTRAP_T_RET16)
1244                         addr += tp->ftt_dest;
1245
1246                 rp->r_rsp = addr;
1247                 new_pc = dst;
1248                 break;
1249         }
1250
1251         case FASTTRAP_T_JCC:
1252         {
1253                 uint_t taken = 0;
1254
1255                 switch (tp->ftt_code) {
1256                 case FASTTRAP_JO:
1257                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_OF) != 0;
1258                         break;
1259                 case FASTTRAP_JNO:
1260                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_OF) == 0;
1261                         break;
1262                 case FASTTRAP_JB:
1263                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_CF) != 0;
1264                         break;
1265                 case FASTTRAP_JAE:
1266                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_CF) == 0;
1267                         break;
1268                 case FASTTRAP_JE:
1269                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_ZF) != 0;
1270                         break;
1271                 case FASTTRAP_JNE:
1272                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_ZF) == 0;
1273                         break;
1274                 case FASTTRAP_JBE:
1275                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_CF) != 0 ||
1276                             (rp->r_rflags & FASTTRAP_EFLAGS_ZF) != 0;
1277                         break;
1278                 case FASTTRAP_JA:
1279                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_CF) == 0 &&
1280                             (rp->r_rflags & FASTTRAP_EFLAGS_ZF) == 0;
1281                         break;
1282                 case FASTTRAP_JS:
1283                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_SF) != 0;
1284                         break;
1285                 case FASTTRAP_JNS:
1286                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_SF) == 0;
1287                         break;
1288                 case FASTTRAP_JP:
1289                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_PF) != 0;
1290                         break;
1291                 case FASTTRAP_JNP:
1292                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_PF) == 0;
1293                         break;
1294                 case FASTTRAP_JL:
1295                         taken = ((rp->r_rflags & FASTTRAP_EFLAGS_SF) == 0) !=
1296                             ((rp->r_rflags & FASTTRAP_EFLAGS_OF) == 0);
1297                         break;
1298                 case FASTTRAP_JGE:
1299                         taken = ((rp->r_rflags & FASTTRAP_EFLAGS_SF) == 0) ==
1300                             ((rp->r_rflags & FASTTRAP_EFLAGS_OF) == 0);
1301                         break;
1302                 case FASTTRAP_JLE:
1303                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_ZF) != 0 ||
1304                             ((rp->r_rflags & FASTTRAP_EFLAGS_SF) == 0) !=
1305                             ((rp->r_rflags & FASTTRAP_EFLAGS_OF) == 0);
1306                         break;
1307                 case FASTTRAP_JG:
1308                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_ZF) == 0 &&
1309                             ((rp->r_rflags & FASTTRAP_EFLAGS_SF) == 0) ==
1310                             ((rp->r_rflags & FASTTRAP_EFLAGS_OF) == 0);
1311                         break;
1312
1313                 }
1314
1315                 if (taken)
1316                         new_pc = tp->ftt_dest;
1317                 else
1318                         new_pc = pc + tp->ftt_size;
1319                 break;
1320         }
1321
1322         case FASTTRAP_T_LOOP:
1323         {
1324                 uint_t taken = 0;
1325 #ifdef __amd64
1326                 greg_t cx = rp->r_rcx--;
1327 #else
1328                 greg_t cx = rp->r_ecx--;
1329 #endif
1330
1331                 switch (tp->ftt_code) {
1332                 case FASTTRAP_LOOPNZ:
1333                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_ZF) == 0 &&
1334                             cx != 0;
1335                         break;
1336                 case FASTTRAP_LOOPZ:
1337                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_ZF) != 0 &&
1338                             cx != 0;
1339                         break;
1340                 case FASTTRAP_LOOP:
1341                         taken = (cx != 0);
1342                         break;
1343                 }
1344
1345                 if (taken)
1346                         new_pc = tp->ftt_dest;
1347                 else
1348                         new_pc = pc + tp->ftt_size;
1349                 break;
1350         }
1351
1352         case FASTTRAP_T_JCXZ:
1353         {
1354 #ifdef __amd64
1355                 greg_t cx = rp->r_rcx;
1356 #else
1357                 greg_t cx = rp->r_ecx;
1358 #endif
1359
1360                 if (cx == 0)
1361                         new_pc = tp->ftt_dest;
1362                 else
1363                         new_pc = pc + tp->ftt_size;
1364                 break;
1365         }
1366
1367         case FASTTRAP_T_PUSHL_EBP:
1368         {
1369                 int ret = 0;
1370
1371 #ifdef __amd64
1372                 if (p->p_model == DATAMODEL_NATIVE) {
1373                         rp->r_rsp -= sizeof (uintptr_t);
1374                         ret = fasttrap_sulword((void *)rp->r_rsp, rp->r_rbp);
1375                 } else {
1376 #endif
1377                         rp->r_rsp -= sizeof (uint32_t);
1378                         ret = fasttrap_suword32((void *)rp->r_rsp, rp->r_rbp);
1379 #ifdef __amd64
1380                 }
1381 #endif
1382
1383                 if (ret == -1) {
1384                         fasttrap_sigsegv(p, curthread, rp->r_rsp);
1385                         new_pc = pc;
1386                         break;
1387                 }
1388
1389                 new_pc = pc + tp->ftt_size;
1390                 break;
1391         }
1392
1393         case FASTTRAP_T_NOP:
1394                 new_pc = pc + tp->ftt_size;
1395                 break;
1396
1397         case FASTTRAP_T_JMP:
1398         case FASTTRAP_T_CALL:
1399                 if (tp->ftt_code == 0) {
1400                         new_pc = tp->ftt_dest;
1401                 } else {
1402                         uintptr_t value, addr = tp->ftt_dest;
1403
1404                         if (tp->ftt_base != FASTTRAP_NOREG)
1405                                 addr += fasttrap_getreg(rp, tp->ftt_base);
1406                         if (tp->ftt_index != FASTTRAP_NOREG)
1407                                 addr += fasttrap_getreg(rp, tp->ftt_index) <<
1408                                     tp->ftt_scale;
1409
1410                         if (tp->ftt_code == 1) {
1411                                 /*
1412                                  * If there's a segment prefix for this
1413                                  * instruction, we'll need to check permissions
1414                                  * and bounds on the given selector, and adjust
1415                                  * the address accordingly.
1416                                  */
1417                                 if (tp->ftt_segment != FASTTRAP_SEG_NONE &&
1418                                     fasttrap_do_seg(tp, rp, &addr) != 0) {
1419                                         fasttrap_sigsegv(p, curthread, addr);
1420                                         new_pc = pc;
1421                                         break;
1422                                 }
1423
1424 #ifdef __amd64
1425                                 if (p->p_model == DATAMODEL_NATIVE) {
1426 #endif
1427                                         if ((value = fasttrap_fulword((void *)addr))
1428                                              == -1) {
1429                                                 fasttrap_sigsegv(p, curthread,
1430                                                     addr);
1431                                                 new_pc = pc;
1432                                                 break;
1433                                         }
1434                                         new_pc = value;
1435 #ifdef __amd64
1436                                 } else {
1437                                         uint32_t value32;
1438                                         addr = (uintptr_t)(uint32_t)addr;
1439                                         if ((value32 = fasttrap_fuword32((void *)addr))
1440                                             == -1) {
1441                                                 fasttrap_sigsegv(p, curthread,
1442                                                     addr);
1443                                                 new_pc = pc;
1444                                                 break;
1445                                         }
1446                                         new_pc = value32;
1447                                 }
1448 #endif
1449                         } else {
1450                                 new_pc = addr;
1451                         }
1452                 }
1453
1454                 /*
1455                  * If this is a call instruction, we need to push the return
1456                  * address onto the stack. If this fails, we send the process
1457                  * a SIGSEGV and reset the pc to emulate what would happen if
1458                  * this instruction weren't traced.
1459                  */
1460                 if (tp->ftt_type == FASTTRAP_T_CALL) {
1461                         int ret = 0;
1462                         uintptr_t addr = 0, pcps;
1463 #ifdef __amd64
1464                         if (p->p_model == DATAMODEL_NATIVE) {
1465                                 addr = rp->r_rsp - sizeof (uintptr_t);
1466                                 pcps = pc + tp->ftt_size;
1467                                 ret = fasttrap_sulword((void *)addr, pcps);
1468                         } else {
1469 #endif
1470                                 addr = rp->r_rsp - sizeof (uint32_t);
1471                                 pcps = (uint32_t)(pc + tp->ftt_size);
1472                                 ret = fasttrap_suword32((void *)addr, pcps);
1473 #ifdef __amd64
1474                         }
1475 #endif
1476
1477                         if (ret == -1) {
1478                                 fasttrap_sigsegv(p, curthread, addr);
1479                                 new_pc = pc;
1480                                 break;
1481                         }
1482
1483                         rp->r_rsp = addr;
1484                 }
1485
1486                 break;
1487
1488         case FASTTRAP_T_COMMON:
1489         {
1490                 uintptr_t addr;
1491 #if defined(__amd64)
1492                 uint8_t scratch[2 * FASTTRAP_MAX_INSTR_SIZE + 22];
1493 #else
1494                 uint8_t scratch[2 * FASTTRAP_MAX_INSTR_SIZE + 7];
1495 #endif
1496                 uint_t i = 0;
1497 #ifdef illumos
1498                 klwp_t *lwp = ttolwp(curthread);
1499
1500                 /*
1501                  * Compute the address of the ulwp_t and step over the
1502                  * ul_self pointer. The method used to store the user-land
1503                  * thread pointer is very different on 32- and 64-bit
1504                  * kernels.
1505                  */
1506 #if defined(__amd64)
1507                 if (p->p_model == DATAMODEL_LP64) {
1508                         addr = lwp->lwp_pcb.pcb_fsbase;
1509                         addr += sizeof (void *);
1510                 } else {
1511                         addr = lwp->lwp_pcb.pcb_gsbase;
1512                         addr += sizeof (caddr32_t);
1513                 }
1514 #else
1515                 addr = USD_GETBASE(&lwp->lwp_pcb.pcb_gsdesc);
1516                 addr += sizeof (void *);
1517 #endif
1518 #else   /* !illumos */
1519                 fasttrap_scrspace_t *scrspace;
1520                 scrspace = fasttrap_scraddr(curthread, tp->ftt_proc);
1521                 if (scrspace == NULL) {
1522                         /*
1523                          * We failed to allocate scratch space for this thread.
1524                          * Try to write the original instruction back out and
1525                          * reset the pc.
1526                          */
1527                         if (fasttrap_copyout(tp->ftt_instr, (void *)pc,
1528                             tp->ftt_size))
1529                                 fasttrap_sigtrap(p, curthread, pc);
1530                         new_pc = pc;
1531                         break;
1532                 }
1533                 addr = scrspace->ftss_addr;
1534 #endif /* illumos */
1535
1536                 /*
1537                  * Generic Instruction Tracing
1538                  * ---------------------------
1539                  *
1540                  * This is the layout of the scratch space in the user-land
1541                  * thread structure for our generated instructions.
1542                  *
1543                  *      32-bit mode                     bytes
1544                  *      ------------------------        -----
1545                  * a:   <original instruction>          <= 15
1546                  *      jmp     <pc + tp->ftt_size>         5
1547                  * b:   <original instruction>          <= 15
1548                  *      int     T_DTRACE_RET                2
1549                  *                                      -----
1550                  *                                      <= 37
1551                  *
1552                  *      64-bit mode                     bytes
1553                  *      ------------------------        -----
1554                  * a:   <original instruction>          <= 15
1555                  *      jmp     0(%rip)                     6
1556                  *      <pc + tp->ftt_size>                 8
1557                  * b:   <original instruction>          <= 15
1558                  *      int     T_DTRACE_RET                2
1559                  *                                      -----
1560                  *                                      <= 46
1561                  *
1562                  * The %pc is set to a, and curthread->t_dtrace_astpc is set
1563                  * to b. If we encounter a signal on the way out of the
1564                  * kernel, trap() will set %pc to curthread->t_dtrace_astpc
1565                  * so that we execute the original instruction and re-enter
1566                  * the kernel rather than redirecting to the next instruction.
1567                  *
1568                  * If there are return probes (so we know that we're going to
1569                  * need to reenter the kernel after executing the original
1570                  * instruction), the scratch space will just contain the
1571                  * original instruction followed by an interrupt -- the same
1572                  * data as at b.
1573                  *
1574                  * %rip-relative Addressing
1575                  * ------------------------
1576                  *
1577                  * There's a further complication in 64-bit mode due to %rip-
1578                  * relative addressing. While this is clearly a beneficial
1579                  * architectural decision for position independent code, it's
1580                  * hard not to see it as a personal attack against the pid
1581                  * provider since before there was a relatively small set of
1582                  * instructions to emulate; with %rip-relative addressing,
1583                  * almost every instruction can potentially depend on the
1584                  * address at which it's executed. Rather than emulating
1585                  * the broad spectrum of instructions that can now be
1586                  * position dependent, we emulate jumps and others as in
1587                  * 32-bit mode, and take a different tack for instructions
1588                  * using %rip-relative addressing.
1589                  *
1590                  * For every instruction that uses the ModRM byte, the
1591                  * in-kernel disassembler reports its location. We use the
1592                  * ModRM byte to identify that an instruction uses
1593                  * %rip-relative addressing and to see what other registers
1594                  * the instruction uses. To emulate those instructions,
1595                  * we modify the instruction to be %rax-relative rather than
1596                  * %rip-relative (or %rcx-relative if the instruction uses
1597                  * %rax; or %r8- or %r9-relative if the REX.B is present so
1598                  * we don't have to rewrite the REX prefix). We then load
1599                  * the value that %rip would have been into the scratch
1600                  * register and generate an instruction to reset the scratch
1601                  * register back to its original value. The instruction
1602                  * sequence looks like this:
1603                  *
1604                  *      64-mode %rip-relative           bytes
1605                  *      ------------------------        -----
1606                  * a:   <modified instruction>          <= 15
1607                  *      movq    $<value>, %<scratch>        6
1608                  *      jmp     0(%rip)                     6
1609                  *      <pc + tp->ftt_size>                 8
1610                  * b:   <modified instruction>          <= 15
1611                  *      int     T_DTRACE_RET                2
1612                  *                                      -----
1613                  *                                         52
1614                  *
1615                  * We set curthread->t_dtrace_regv so that upon receiving
1616                  * a signal we can reset the value of the scratch register.
1617                  */
1618
1619                 ASSERT(tp->ftt_size < FASTTRAP_MAX_INSTR_SIZE);
1620
1621                 curthread->t_dtrace_scrpc = addr;
1622                 bcopy(tp->ftt_instr, &scratch[i], tp->ftt_size);
1623                 i += tp->ftt_size;
1624
1625 #ifdef __amd64
1626                 if (tp->ftt_ripmode != 0) {
1627                         greg_t *reg = NULL;
1628
1629                         ASSERT(p->p_model == DATAMODEL_LP64);
1630                         ASSERT(tp->ftt_ripmode &
1631                             (FASTTRAP_RIP_1 | FASTTRAP_RIP_2));
1632
1633                         /*
1634                          * If this was a %rip-relative instruction, we change
1635                          * it to be either a %rax- or %rcx-relative
1636                          * instruction (depending on whether those registers
1637                          * are used as another operand; or %r8- or %r9-
1638                          * relative depending on the value of REX.B). We then
1639                          * set that register and generate a movq instruction
1640                          * to reset the value.
1641                          */
1642                         if (tp->ftt_ripmode & FASTTRAP_RIP_X)
1643                                 scratch[i++] = FASTTRAP_REX(1, 0, 0, 1);
1644                         else
1645                                 scratch[i++] = FASTTRAP_REX(1, 0, 0, 0);
1646
1647                         if (tp->ftt_ripmode & FASTTRAP_RIP_1)
1648                                 scratch[i++] = FASTTRAP_MOV_EAX;
1649                         else
1650                                 scratch[i++] = FASTTRAP_MOV_ECX;
1651
1652                         switch (tp->ftt_ripmode) {
1653                         case FASTTRAP_RIP_1:
1654                                 reg = &rp->r_rax;
1655                                 curthread->t_dtrace_reg = REG_RAX;
1656                                 break;
1657                         case FASTTRAP_RIP_2:
1658                                 reg = &rp->r_rcx;
1659                                 curthread->t_dtrace_reg = REG_RCX;
1660                                 break;
1661                         case FASTTRAP_RIP_1 | FASTTRAP_RIP_X:
1662                                 reg = &rp->r_r8;
1663                                 curthread->t_dtrace_reg = REG_R8;
1664                                 break;
1665                         case FASTTRAP_RIP_2 | FASTTRAP_RIP_X:
1666                                 reg = &rp->r_r9;
1667                                 curthread->t_dtrace_reg = REG_R9;
1668                                 break;
1669                         }
1670
1671                         /* LINTED - alignment */
1672                         *(uint64_t *)&scratch[i] = *reg;
1673                         curthread->t_dtrace_regv = *reg;
1674                         *reg = pc + tp->ftt_size;
1675                         i += sizeof (uint64_t);
1676                 }
1677 #endif
1678
1679                 /*
1680                  * Generate the branch instruction to what would have
1681                  * normally been the subsequent instruction. In 32-bit mode,
1682                  * this is just a relative branch; in 64-bit mode this is a
1683                  * %rip-relative branch that loads the 64-bit pc value
1684                  * immediately after the jmp instruction.
1685                  */
1686 #ifdef __amd64
1687                 if (p->p_model == DATAMODEL_LP64) {
1688                         scratch[i++] = FASTTRAP_GROUP5_OP;
1689                         scratch[i++] = FASTTRAP_MODRM(0, 4, 5);
1690                         /* LINTED - alignment */
1691                         *(uint32_t *)&scratch[i] = 0;
1692                         i += sizeof (uint32_t);
1693                         /* LINTED - alignment */
1694                         *(uint64_t *)&scratch[i] = pc + tp->ftt_size;
1695                         i += sizeof (uint64_t);
1696                 } else {
1697 #endif
1698                         /*
1699                          * Set up the jmp to the next instruction; note that
1700                          * the size of the traced instruction cancels out.
1701                          */
1702                         scratch[i++] = FASTTRAP_JMP32;
1703                         /* LINTED - alignment */
1704                         *(uint32_t *)&scratch[i] = pc - addr - 5;
1705                         i += sizeof (uint32_t);
1706 #ifdef __amd64
1707                 }
1708 #endif
1709
1710                 curthread->t_dtrace_astpc = addr + i;
1711                 bcopy(tp->ftt_instr, &scratch[i], tp->ftt_size);
1712                 i += tp->ftt_size;
1713                 scratch[i++] = FASTTRAP_INT;
1714                 scratch[i++] = T_DTRACE_RET;
1715
1716                 ASSERT(i <= sizeof (scratch));
1717
1718 #ifdef illumos
1719                 if (fasttrap_copyout(scratch, (char *)addr, i)) {
1720 #else
1721                 if (uwrite(p, scratch, i, addr)) {
1722 #endif
1723                         fasttrap_sigtrap(p, curthread, pc);
1724                         new_pc = pc;
1725                         break;
1726                 }
1727                 if (tp->ftt_retids != NULL) {
1728                         curthread->t_dtrace_step = 1;
1729                         curthread->t_dtrace_ret = 1;
1730                         new_pc = curthread->t_dtrace_astpc;
1731                 } else {
1732                         new_pc = curthread->t_dtrace_scrpc;
1733                 }
1734
1735                 curthread->t_dtrace_pc = pc;
1736                 curthread->t_dtrace_npc = pc + tp->ftt_size;
1737                 curthread->t_dtrace_on = 1;
1738                 break;
1739         }
1740
1741         default:
1742                 panic("fasttrap: mishandled an instruction");
1743         }
1744
1745 done:
1746         /*
1747          * If there were no return probes when we first found the tracepoint,
1748          * we should feel no obligation to honor any return probes that were
1749          * subsequently enabled -- they'll just have to wait until the next
1750          * time around.
1751          */
1752         if (tp->ftt_retids != NULL) {
1753                 /*
1754                  * We need to wait until the results of the instruction are
1755                  * apparent before invoking any return probes. If this
1756                  * instruction was emulated we can just call
1757                  * fasttrap_return_common(); if it needs to be executed, we
1758                  * need to wait until the user thread returns to the kernel.
1759                  */
1760                 if (tp->ftt_type != FASTTRAP_T_COMMON) {
1761                         /*
1762                          * Set the program counter to the address of the traced
1763                          * instruction so that it looks right in ustack()
1764                          * output. We had previously set it to the end of the
1765                          * instruction to simplify %rip-relative addressing.
1766                          */
1767                         rp->r_rip = pc;
1768
1769                         fasttrap_return_common(rp, pc, pid, new_pc);
1770                 } else {
1771                         ASSERT(curthread->t_dtrace_ret != 0);
1772                         ASSERT(curthread->t_dtrace_pc == pc);
1773                         ASSERT(curthread->t_dtrace_scrpc != 0);
1774                         ASSERT(new_pc == curthread->t_dtrace_astpc);
1775                 }
1776         }
1777
1778         rp->r_rip = new_pc;
1779
1780 #ifndef illumos
1781         PROC_LOCK(p);
1782         proc_write_regs(curthread, rp);
1783         PROC_UNLOCK(p);
1784 #endif
1785
1786         return (0);
1787 }
1788
1789 int
1790 fasttrap_return_probe(struct reg *rp)
1791 {
1792         proc_t *p = curproc;
1793         uintptr_t pc = curthread->t_dtrace_pc;
1794         uintptr_t npc = curthread->t_dtrace_npc;
1795
1796         curthread->t_dtrace_pc = 0;
1797         curthread->t_dtrace_npc = 0;
1798         curthread->t_dtrace_scrpc = 0;
1799         curthread->t_dtrace_astpc = 0;
1800
1801 #ifdef illumos
1802         /*
1803          * Treat a child created by a call to vfork(2) as if it were its
1804          * parent. We know that there's only one thread of control in such a
1805          * process: this one.
1806          */
1807         while (p->p_flag & SVFORK) {
1808                 p = p->p_parent;
1809         }
1810 #endif
1811
1812         /*
1813          * We set rp->r_rip to the address of the traced instruction so
1814          * that it appears to dtrace_probe() that we're on the original
1815          * instruction, and so that the user can't easily detect our
1816          * complex web of lies. dtrace_return_probe() (our caller)
1817          * will correctly set %pc after we return.
1818          */
1819         rp->r_rip = pc;
1820
1821         fasttrap_return_common(rp, pc, p->p_pid, npc);
1822
1823         return (0);
1824 }
1825
1826 /*ARGSUSED*/
1827 uint64_t
1828 fasttrap_pid_getarg(void *arg, dtrace_id_t id, void *parg, int argno,
1829     int aframes)
1830 {
1831         struct reg r;
1832
1833         fill_regs(curthread, &r);
1834
1835         return (fasttrap_anarg(&r, 1, argno));
1836 }
1837
1838 /*ARGSUSED*/
1839 uint64_t
1840 fasttrap_usdt_getarg(void *arg, dtrace_id_t id, void *parg, int argno,
1841     int aframes)
1842 {
1843         struct reg r;
1844
1845         fill_regs(curthread, &r);
1846
1847         return (fasttrap_anarg(&r, 0, argno));
1848 }
1849
1850 static ulong_t
1851 fasttrap_getreg(struct reg *rp, uint_t reg)
1852 {
1853 #ifdef __amd64
1854         switch (reg) {
1855         case REG_R15:           return (rp->r_r15);
1856         case REG_R14:           return (rp->r_r14);
1857         case REG_R13:           return (rp->r_r13);
1858         case REG_R12:           return (rp->r_r12);
1859         case REG_R11:           return (rp->r_r11);
1860         case REG_R10:           return (rp->r_r10);
1861         case REG_R9:            return (rp->r_r9);
1862         case REG_R8:            return (rp->r_r8);
1863         case REG_RDI:           return (rp->r_rdi);
1864         case REG_RSI:           return (rp->r_rsi);
1865         case REG_RBP:           return (rp->r_rbp);
1866         case REG_RBX:           return (rp->r_rbx);
1867         case REG_RDX:           return (rp->r_rdx);
1868         case REG_RCX:           return (rp->r_rcx);
1869         case REG_RAX:           return (rp->r_rax);
1870         case REG_TRAPNO:        return (rp->r_trapno);
1871         case REG_ERR:           return (rp->r_err);
1872         case REG_RIP:           return (rp->r_rip);
1873         case REG_CS:            return (rp->r_cs);
1874         case REG_RFL:           return (rp->r_rflags);
1875         case REG_RSP:           return (rp->r_rsp);
1876         case REG_SS:            return (rp->r_ss);
1877         case REG_FS:            return (rp->r_fs);
1878         case REG_GS:            return (rp->r_gs);
1879         case REG_DS:            return (rp->r_ds);
1880         case REG_ES:            return (rp->r_es);
1881         case REG_FSBASE:        return (rdmsr(MSR_FSBASE));
1882         case REG_GSBASE:        return (rdmsr(MSR_GSBASE));
1883         }
1884
1885         panic("dtrace: illegal register constant");
1886         /*NOTREACHED*/
1887 #else
1888 #define _NGREG 19
1889         if (reg >= _NGREG)
1890                 panic("dtrace: illegal register constant");
1891
1892         return (((greg_t *)&rp->r_gs)[reg]);
1893 #endif
1894 }